Special Issue "ZnO and TiO2 Based Nanostructures"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (30 September 2017)

Special Issue Editor

Guest Editor
Dr. Andrea Lamberti

Politecnico di Torino, Torino, Italy
Website1 | Website2 | E-Mail
Interests: metal-oxide nanostructures; TiO2 nanotubes; graphene; supercapacitors; nanotechnology; dye-sensitized solar cells

Special Issue Information

Dear Colleagues,

Transition-metal oxide nanostructures are the focus of current research efforts in nanotechnology since they are the most common minerals on Earth, and also thanks to their special shapes, compositions, and chemical and physical properties. They have now been widely used in the design of energy saving and harvesting devices, such as lithium-ion batteries, fuel cells, solar cells, and even transistors, light emitting devices (LEDs), hydrogen production by water photolysis and its storage, water and air purification by degradation of organic/inorganic pollutants, bio-sensing devices, environmental monitoring by their applications in the fabrication of gas, humidity, and temperature sensors, and photodetectors.

In addition to the great application potentials, oxide-based nanomaterials, such as ZnO and TiO2, have recently revolutionized nanomaterial research thanks to their outstanding properties. They can be produced in different shapes (such as nanowires, nanobelts, nanorods, nanotubes, nanocombs, nanorings, nanohelixes/nanosprings, nanocages and nanosheets, and nanostars) depending on the synthesis routes, which range in techniques.

This Special Issue of Nanomaterials will attempt to cover the most recent advances in ZnO and TiO2 nanostructures, concerning, not only the synthesis and characterization, but especially reports of their functional and smart properties to be applied in working devices. Applications of nanosized ZnO and TiO2 can range widely, from biomedical and drug delivery devices to piezoelectric and chemical sensors, and energy harvesting, conversion and storage devices.

Dr. Andrea Lamberti
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Advanced synthesis
  • Smart properties
  • Characterizations
  • Multifunctional materials
  • Energy harvesting/storage device
  • Sensors
  • Bio-materials and bio-devices

Published Papers (11 papers)

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Research

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Open AccessArticle Enhanced UV-Visible Light Photocatalytic Activity by Constructing Appropriate Heterostructures between Mesopore TiO2 Nanospheres and Sn3O4 Nanoparticles
Nanomaterials 2017, 7(10), 336; doi:10.3390/nano7100336 (registering DOI)
Received: 25 September 2017 / Revised: 12 October 2017 / Accepted: 13 October 2017 / Published: 19 October 2017
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Abstract
Novel TiO2/Sn3O4 heterostructure photocatalysts were ingeniously synthesized via a scalable two-step method. The impressive photocatalytic abilities of the TiO2/Sn3O4 sphere nanocomposites were validated by the degradation test of methyl orange and •OH trapping
[...] Read more.
Novel TiO2/Sn3O4 heterostructure photocatalysts were ingeniously synthesized via a scalable two-step method. The impressive photocatalytic abilities of the TiO2/Sn3O4 sphere nanocomposites were validated by the degradation test of methyl orange and •OH trapping photoluminescence experiments under ultraviolet (UV) and visible light irradiation, respectively. Especially under the visible light, the TiO2/Sn3O4 nanocomposites demonstrated a superb photocatalytic activity, with 81.2% of methyl orange (MO) decomposed at 30 min after irradiation, which greatly exceeded that of the P25 (13.4%), TiO2 (0.5%) and pure Sn3O4 (59.1%) nanostructures. This enhanced photocatalytic performance could be attributed to the mesopore induced by the monodispersed TiO2 cores that supply sufficient surface areas and accessibility to reactant molecules. This exquisite hetero-architecture facilitates extended UV-visible absorption and efficient photoexcited charge carrier separation. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Microstructuring of Mesoporous Titania Films Loaded with Silver Salts to Enhance the Photocatalytic Degradation of Methyl Blue under Visible Light
Nanomaterials 2017, 7(10), 334; doi:10.3390/nano7100334
Received: 22 September 2017 / Revised: 29 September 2017 / Accepted: 5 October 2017 / Published: 17 October 2017
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Abstract
The microstructuring of the distribution of silver nanoparticles (NPs) in mesoporous titania films loaded with silver salts, using two-beam interference lithography leading to 1 Dimension (1D) grating, induces variations in the photocatalytic efficiency. The influence of the structuration was tested on the degradation
[...] Read more.
The microstructuring of the distribution of silver nanoparticles (NPs) in mesoporous titania films loaded with silver salts, using two-beam interference lithography leading to 1 Dimension (1D) grating, induces variations in the photocatalytic efficiency. The influence of the structuration was tested on the degradation of methyl blue (MB) under ultraviolet (UV) and visible illumination, giving rise to a significant improvement of the photocatalytic efficiency. The periodic distribution of the NPs was characterized by transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM). Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle TiO2 Nanowire Networks Prepared by Titanium Corrosion and Their Application to Bendable Dye-Sensitized Solar Cells
Nanomaterials 2017, 7(10), 315; doi:10.3390/nano7100315
Received: 10 August 2017 / Revised: 20 September 2017 / Accepted: 25 September 2017 / Published: 12 October 2017
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Abstract
TiO2 nanowire networks were prepared, using the corrosion of Ti foils in alkaline (potassium hydroxide, KOH) solution at different temperatures, and then a further ion-exchange process. The prepared nanostructures were characterized by field emission scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron
[...] Read more.
TiO2 nanowire networks were prepared, using the corrosion of Ti foils in alkaline (potassium hydroxide, KOH) solution at different temperatures, and then a further ion-exchange process. The prepared nanostructures were characterized by field emission scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The wet corroded foils were utilized as the photoanodes of bendable dye-sensitized solar cells (DSSCs), which exhibited a power conversion efficiency of 1.11% under back illumination. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Periodic TiO2 Nanostructures with Improved Aspect and Line/Space Ratio Realized by Colloidal Photolithography Technique
Nanomaterials 2017, 7(10), 316; doi:10.3390/nano7100316
Received: 11 September 2017 / Revised: 29 September 2017 / Accepted: 5 October 2017 / Published: 12 October 2017
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Abstract
This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures—in this case, hexagonally arranged nanopillars—printed in a layer of directly photopatternable sol-gel TiO2. Firstly,
[...] Read more.
This paper presents substantial improvements of the colloidal photolithography technique (also called microsphere lithography) with the goal of better controlling the geometry of the fabricated nano-scale structures—in this case, hexagonally arranged nanopillars—printed in a layer of directly photopatternable sol-gel TiO2. Firstly, to increase the achievable structure height the photosensitive layer underneath the microspheres is deposited on a reflective layer instead of the usual transparent substrate. Secondly, an increased width of the pillars is achieved by tilting the incident wave and using multiple exposures or substrate rotation, additionally allowing to better control the shape of the pillar’s cross section. The theoretical analysis is carried out by rigorous modelling of the photonics nanojet underneath the microspheres and by optimizing the experimental conditions. Aspect ratios (structure height/lateral structure size) greater than 2 are predicted and demonstrated experimentally for structure dimensions in the sub micrometer range, as well as line/space ratios (lateral pillar size/distance between pillars) greater than 1. These nanostructures could lead for example to materials exhibiting efficient light trapping in the visible and near-infrared range, as well as improved hydrophobic or photocatalytic properties for numerous applications in environmental and photovoltaic systems. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Tuning the Electronic Conductivity in Hydrothermally Grown Rutile TiO2 Nanowires: Effect of Heat Treatment in Different Environments
Nanomaterials 2017, 7(10), 289; doi:10.3390/nano7100289
Received: 28 August 2017 / Revised: 13 September 2017 / Accepted: 19 September 2017 / Published: 23 September 2017
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Abstract
Hydrothermally grown rutile TiO2 nanowires are intrinsically full of lattice defects, especially oxygen vacancies. These vacancies have a significant influence on the structural and electronic properties of the nanowires. In this study, we report a post-growth heat treatment in different environments that
[...] Read more.
Hydrothermally grown rutile TiO2 nanowires are intrinsically full of lattice defects, especially oxygen vacancies. These vacancies have a significant influence on the structural and electronic properties of the nanowires. In this study, we report a post-growth heat treatment in different environments that allows control of the distribution of these defects inside the nanowire, and thus gives direct access to tuning of the properties of rutile TiO2 nanowires. A detailed transmission electron microscopy study is used to analyze the structural changes inside the nanowires which are correlated to the measured optical and electrical properties. The highly defective as-grown nanowire arrays have a white appearance and show typical semiconducting properties with n-type conductivity, which is related to the high density of oxygen vacancies. Heat treatment in air atmosphere leads to a vacancy condensation and results in nanowires which possess insulating properties, whereas heat treatment in N2 atmosphere leads to nanowire arrays that appear black and show almost metal-like conductivity. We link this high conductivity to a TiO2−x shell which forms during the annealing process due to the slightly reducing N2 environment. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle In Vitro Sonodynamic Therapeutic Effect of Polyion Complex Micelles Incorporating Titanium Dioxide Nanoparticles
Nanomaterials 2017, 7(9), 268; doi:10.3390/nano7090268
Received: 1 August 2017 / Revised: 28 August 2017 / Accepted: 6 September 2017 / Published: 11 September 2017
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Abstract
Titanium dioxide nanoparticles (TiO2 NPs) can act as sonosensitizers, generating reactive oxygen species under ultrasound irradiation, for use in sonodynamic therapy. For TiO2 NPs delivery, we prepared polyion complex micelles incorporating TiO2 NPs (TiO2 NPs-PIC micelles) by mixing TiO
[...] Read more.
Titanium dioxide nanoparticles (TiO2 NPs) can act as sonosensitizers, generating reactive oxygen species under ultrasound irradiation, for use in sonodynamic therapy. For TiO2 NPs delivery, we prepared polyion complex micelles incorporating TiO2 NPs (TiO2 NPs-PIC micelles) by mixing TiO2 NPs with polyallylamine bearing poly(ethylene glycol) grafts. In this study, the effects of polymer composition and ultrasound irradiation conditions on the sonodynamic therapeutic effect toward HeLa cells were evaluated experimentally using cell viability evaluation, intracellular distribution observation, and a cell staining assay. TiO2 NPs-PIC micelles with widely distributed features induced a significant decrease in cell viability under ultrasound irradiation. Furthermore, prolonging the irradiation time killed cells more effectively than did increasing the ultrasound power. The combination of TiO2 NP-PIC micelles and ultrasound irradiation was confirmed to induce apoptotic cell death. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Growth Method-Dependent and Defect Density-Oriented Structural, Optical, Conductive, and Physical Properties of Solution-Grown ZnO Nanostructures
Nanomaterials 2017, 7(9), 266; doi:10.3390/nano7090266
Received: 1 August 2017 / Revised: 28 August 2017 / Accepted: 7 September 2017 / Published: 10 September 2017
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Abstract
It is time for industry to pay a serious heed to the application and quality-dependent research on the most important solution growth methods for ZnO, namely, aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. This study proffers a critical analysis on how
[...] Read more.
It is time for industry to pay a serious heed to the application and quality-dependent research on the most important solution growth methods for ZnO, namely, aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. This study proffers a critical analysis on how the defect density and formation behavior of ZnO nanostructures (ZNSs) are growth method-dependent. Both antithetical and facile methods are exploited to control the ZnO defect density and the growth mechanism. In this context, the growth of ZnO nanorods (ZNRs), nanoflowers, and nanotubes (ZNTs) are considered. The aforementioned growth methods directly stimulate the nanostructure crystal growth and, depending upon the defect density, ZNSs show different trends in structural, optical, etching, and conductive properties. The defect density of MAG ZNRs is the least because of an ample amount of thermal energy catered by high-power microwaves to the atoms to grow on appropriate crystallographic planes, which is not the case in faulty convective ACG ZNSs. Defect-centric etching of ZNRs into ZNTs is also probed and methodological constraints are proposed. ZNS optical properties are different in the visible region, which are quite peculiar, but outstanding for ZNRs. Hall effect measurements illustrate incongruent conductive trends in both samples. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Preparation and Characterization of ZnO Nanoparticles Supported on Amorphous SiO2
Nanomaterials 2017, 7(8), 217; doi:10.3390/nano7080217
Received: 30 June 2017 / Revised: 21 July 2017 / Accepted: 24 July 2017 / Published: 10 August 2017
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Abstract
In order to reduce the primary particle size of zinc oxide (ZnO) and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2) by the hydrogen bond association between hydroxyl groups
[...] Read more.
In order to reduce the primary particle size of zinc oxide (ZnO) and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2) by the hydrogen bond association between hydroxyl groups in the hydrothermal process. After calcining the precursors, dehydration condensation among hydroxyl groups occurred and ZnO nanoparticles supported on amorphous SiO2 (ZnO–SiO2) were prepared. Furthermore, the SEM and TEM observations showed that ZnO nanoparticles with a particle size of 3–8 nm were uniformly and dispersedly loaded on the surface of amorphous SiO2. Compared with pure ZnO, ZnO–SiO2 showed a much better antibacterial performance in the minimum inhibitory concentration (MIC) test and the antibacterial properties of the paint adding ZnO–SiO2 composite. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Growth Mechanism Studies of ZnO Nanowires: Experimental Observations and Short-Circuit Diffusion Analysis
Nanomaterials 2017, 7(7), 188; doi:10.3390/nano7070188
Received: 3 July 2017 / Revised: 18 July 2017 / Accepted: 18 July 2017 / Published: 21 July 2017
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Abstract
Plenty of studies have been performed to probe the diverse properties of ZnO nanowires, but only a few have focused on the physical properties of a single nanowire since analyzing the growth mechanism along a single nanowire is difficult. In this study, a
[...] Read more.
Plenty of studies have been performed to probe the diverse properties of ZnO nanowires, but only a few have focused on the physical properties of a single nanowire since analyzing the growth mechanism along a single nanowire is difficult. In this study, a single ZnO nanowire was synthesized using a Ti-assisted chemical vapor deposition (CVD) method to avoid the appearance of catalytic contamination. Two-dimensional energy dispersive spectroscopy (EDS) mapping with a diffusion model was used to obtain the diffusion length and the activation energy ratio. The ratio value is close to 0.3, revealing that the growth of ZnO nanowires was attributed to the short-circuit diffusion. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Open AccessArticle Oxygen Partial Pressure Impact on Characteristics of Indium Titanium Zinc Oxide Thin Film Transistor Fabricated via RF Sputtering
Nanomaterials 2017, 7(7), 156; doi:10.3390/nano7070156
Received: 21 April 2017 / Revised: 23 June 2017 / Accepted: 23 June 2017 / Published: 26 June 2017
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Abstract
Indium titanium zinc oxide (InTiZnO) as the channel layer in thin film transistor (TFT) grown by RF sputtering system is proposed in this work. Optical and electrical properties were investigated. By changing the oxygen flow ratio, we can suppress excess and undesirable oxygen-related
[...] Read more.
Indium titanium zinc oxide (InTiZnO) as the channel layer in thin film transistor (TFT) grown by RF sputtering system is proposed in this work. Optical and electrical properties were investigated. By changing the oxygen flow ratio, we can suppress excess and undesirable oxygen-related defects to some extent, making it possible to fabricate the optimized device. XPS patterns for O 1s of InTiZnO thin films indicated that the amount of oxygen vacancy was apparently declined with the increasing oxygen flow ratio. The fabricated TFTs showed a threshold voltage of −0.9 V, mobility of 0.884 cm2/Vs, on-off ratio of 5.5 × 105, and subthreshold swing of 0.41 V/dec. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Review

Jump to: Research

Open AccessReview Wet-Chemical Preparation of TiO2-Based Composites with Different Morphologies and Photocatalytic Properties
Nanomaterials 2017, 7(10), 310; doi:10.3390/nano7100310
Received: 7 September 2017 / Revised: 30 September 2017 / Accepted: 2 October 2017 / Published: 9 October 2017
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Abstract
TiO2-based composites have been paid significant attention in the photocatalysis field. The size, crystallinity and nanomorphology of TiO2 materials have an important effect on the photocatalytic efficiency. The synthesis and photocatalytic activity of TiO2-based materials have been widely
[...] Read more.
TiO2-based composites have been paid significant attention in the photocatalysis field. The size, crystallinity and nanomorphology of TiO2 materials have an important effect on the photocatalytic efficiency. The synthesis and photocatalytic activity of TiO2-based materials have been widely investigated in past decades. Based on our group’s research works on TiO2 materials, this review introduces several methods for the fabrication of TiO2, rare-earth-doped TiO2 and noble-metal-decorated TiO2 particles with different morphologies. We focused on the preparation and the formation mechanism of TiO2-based materials with unique structures including spheres, hollow spheres, porous spheres, hollow porous spheres and urchin-like spheres. The photocatalytical activity of urchin-like TiO2, noble metal nanoparticle-decorated 3D (three-dimensional) urchin-like TiO2 and bimetallic core/shell nanoparticle-decorated urchin-like hierarchical TiO2 are briefly discussed. Full article
(This article belongs to the Special Issue ZnO and TiO2 Based Nanostructures)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of paper: Full paper
Tentative title: Time- and concentration-dependent evaluation of lipid-coated zinc oxide nanocrystals as photodynamic therapeutics in cancer cells
Short abstract: In the present paper we use zinc oxide nanocrystalline particles under the excitation of ultraviolet light for the generation of highly cytotoxic reactive oxygen species, with the aim of fighting cancer cells in vitro. Owing to the difficulties in obtaining highly dispersed nanocrystals (NCs) in biological media, we propose their coating with a double-lipidic bilayer and we evaluate their colloidal stability, cell internalization and cytotoxic behaviour in comparison to the bare zinc oxide NCs. By systematically varying the concentration of NCs and the application time of ultraviolet light, we measure the type and amount of generated reactive oxygen species (ROS) by Electron Paramagnetic Resonance (EPR) spectroscopy. We finally evaluate the cytotoxic effect toward HeLa Cancer cells, showing promising results for the development of potential ZnO-based therapeutic systems.

Article Type: Review
Title: Engineering the Surface/Interface Structures of Titanium Dioxide Micro/Nano Architectures towards Environmental and Electrochemical Applications
Authors: Xiaoliang Wang 1,*, Yanyan Zhao 2 and Hongyu Sun 3,*
Affiliation: 1 College of Science, Hebei University of Science and Technology, Shijiazhuang 050018, PR China; wxlsr@126.com (X. W.)
2 Department of Chemistry Boston College Merkert Chemistry Center, 2609 Beacon St., Chestnut Hill, Massachusetts 02467, USA; zhaogh@bc.edu (Y. Z.)
3 Department of Micro- and Nanotechnology, Technical University of Denmark, Kongens Lyngby 2800, Denmark; hsun@nanotech.dtu.dk (H. S.)
Correspondence: wxlsr@126.com; hsun@nanotech.dtu.dk; Tel.: +45-45 25 68 40 (H. S.)
Abstract: Titanium Dioxide (TiO2) micro/nano architectures have been intensively studied in the past years because of the applications in environmental, energy conversion, and storage fields, such as heterogeneous catalysis, dye-sensitized solar cells, lithium/sodium ion batteries, lithium sulfur batteries, sensors, bio-nanotechnology, etc. Surface and/or interface structures in the TiO2 micro/nano architectures play important roles in those applications. This mini review article focuses on TiO2 micro/nano architectures with typical crystal structures (anatase, rutile, brookite, and TiO2(B)), and summarizes major advances in the surface/interface engineering, characterization, applications in environment and electrochemical devices. We present the principles and growth mechanisms of TiO2 nanostructures via different methods, with an emphasis on rational control of the surface and interface structures. We next discuss the applications of TiO2 micro/nano architectures in photocatalytic degradation of organic contaminants in water, electrochemical sensor, lithium/sodium ion batteries, and lithium sulfur batteries. Throughout the discussion, the relationship between the device performance and the surface/interface structures of TiO2 micro/nano structures will be highlighted. Then we discuss the phase transitions of TiO2 nanostructures and possible strategies of improving the phase stability. This review concludes with a personal perspective on the current challenges and future researches.
Keywords: titanium oxide; crystal structure; surface/interface structures; photocatalytic degradation; sensor; lithium ion battery

Title: Photocatalytic properties of zinc oxide hierarchical structures electrodeposited on metallic web electrodes
Authors: Elena Matei, Cristina Busuioc, Mihaela Oancea, Alexandru Evanghelidis, Camelia Florica, Monica Enculescu, Ionut Enculescu*
*Corresponding author:
National Institute for Materials Physics, Magurele, Ilfov, Romania, RO-077125
Abstract: Metallic web electrodes were prepared by electrospinning poly(methyl methacrylate) fibers onto metal frame collectors and subsequent metallization by DC sputtering. These were thermally transferred onto glass substrates and employed as working electrodes for the electrochemical deposition of ZnO. The transparency of the webs, a function of fiber density, is comparable to that of conventional transparent conductive oxides.
Figure 1. The steps in preparing the substrates for ZnO electrodeposition: (a) as-spun PMMA web, (b) gold covered web, (c) glass substrate covered with the metallic web electrode (the two gold stripes were sputtered on glass for a better clamping contact when performing the electrodeposition) and (d) microscopic detail of the metal covered PMMA web.
As well, the same enhanced control of the ZnO electroplating process was observed for the case of using web electrodes as for performing deposition on transparent conducting oxides or on metal substrates electrodes. Structural, optical and morphological properties were investigated and correlated to the electrodeposition conditions. Such hierarchically structured electrodes can be employed in a wide range of applications where flexible transparent conducting layers are required.
Figure 2. SEM images of ZnO nanorods deposited on metallic web electrodes from bath containing 0.5 mM Zn(NO3)2 and 100 mM KNO3
One example of such application is related to the photocatalytic activity of ZnO coated fibers. This was analyzed by studying the photodegradation of methylene blue films under UV irradiation.

Title: In Vitro Sonodynamic Therapeutic Effect of Polyion Complex Micelles Incorporating Titanium Dioxide Nanoparticles
Authors: Satoshi Yamamoto, Masafumi Ono, Eiji Yuba, Atsushi Harada* and Kenji Kono
Abstract: Titanium dioxide nanoparticles (TiO2 NPs) has available ability to act as a sonosensitizer, which can generate reactive oxygen species by ultrasound irradiation, for sonodynamic therapy. For the delivery of TiO2 NPs, we prepared polyion complex micelles incorporating TiO2 NPs (TiO2 NPs-PIC micelles) by mixing TiO2 NPs and polyallylamine bearing poly(ethylene glycol) grafts. In this study, the effect of polymer composition and ultrasound irradiation condition to sonodynamic therapeutic effect toward HeLa cells were evaluated through the experiments including the evaluation of cell viability, the observation of intracellular distribution and cell staining assay. TiO2 NPs-PIC micelles with widely-distributed feature induced a significant decrease in cell viability by ultrasound irradiation. Also, the prolongation of irradiation time provided more effective cell-killing compared with an increase in ultrasound power. Further, it was confirmed that the combination of TiO2 NPs-PIC micelles and ultrasound irradiation induced apoptotic cell death.

Title: ZnO nanowire synthesis and application in sensing
Author: Guido Viscardi
Abstract: This article will provide a comprehensive review of the state-of-the-art research activities focused on the advanced synthesis and application of ZnO nanowires (NWs) for sensing. In the beginning synthesis methods are briefly introduced, namely hydrothermal and vapor phase methods, demonstrating approaches for controlled synthesis of different ZnO NW morphology and further methods for ZnO NW surface modification, discussing how this effects the sensing. Next, UV and gas sensing mechanisms are briefly discussed, sensor types: single nanowire, nanowire junction (or Schottky contact) and p-n junction sensors are described. Further, novel approaches for sensing, using ZnO NW hybrid structures with other materials, such as metal nanoparticles or carbon nanomaterials will be demonstrated, limiting factors and possible improvement will be discussed . The review will then conclude with some perspectives and outlook on the future developments in the ZnO NW application for sensing.

Title: Resistive Switching of 5 nm TiO2 Nanoparticle Self-Assembled Monolayers
Authors: Dirk Oliver Schmidt 1,2, Nicolas Raab 3,4, Michael Noyong 1,2, Venugopal Santhanam 5, R. Dittmann 3,4 and Ulrich Simon 1,2,*
Affiliations: 1 JARA-FIT, 52056 Aachen, Germany;
2
Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany;
3
JARA-FIT, 52425 Jülich, Germany;
4
Peter Grünberg Institut 7, Forschungszentrum Jülich GmbH, Jülich, 52428, Germany;
5
Department of Chemical Engineering, Indian Institute of Science, Bangalore, India-560012;
Correspondance: ; Tel.: +49-241-80-94644
Abstract: Resistively switching devices are promising candidates for the next generation of non-volatile data memories. Such devices are up to now fabricated mainly by means of top-down approaches applying thin films sandwiched between electrodes. Recent works have demonstrated that resistive switching (RS) gets feasible also on chemically synthesized nanoparticles (NPs) in the 50 nm range. By following this concept, we developed this approach further to the sub-10 nm range. In this work, we report RS of 5 nm TiO2 NPs that were self-assembled into monolayers and transferred on metallic substrates. We electrically characterized these monolayers in regard to their RS properties by means of a nanorobotics system in a scanning electron microscope and found typical features of bipolar resistive switching.

Title: Soft synthesis of N-doped yellow anatase nanoparticles
Authors: David G. Calatayud1, Raquel M. Flores1,2, Amador C. Caballero1, Teresa Jardiel1
Affiliation: 1 Department of Electroceramics, Instituto de Cerámica y Vidrio – CSIC, Kelsen 5, Campus de Cantoblanco, 28049, Madrid, Spain
2 Universidad Rey Juan Carlos, Avda. de Atenas, s/n 28922 Alcorcón, Madrid
Abstract: Titanium dioxide has become a material of great interest, both form a scientific and technological point of view, due to its excellent optical and electronic properties, a strong oxidising power, chemical stability and low toxicity. These characteristics make it a good candidate to be used in various fields, among which is the photocatalysis. In this sense, the properties of TiO2 can be modulated through precise control of crystallinity, crystalline phase, shape and size of the particles together with the band-gap engineering. In this work, nanoparticles with controlled size and crystallinity have been synthesized using a solvothermal process under different reaction conditions and urea as a doping agent. N-doped yellow pure anatase nanoparticles have been obtained with a reduce band gap (< 3.0 eV), increasing the light absorption range of TiO2 nanoparticles. In addition, this synthetic method allows a high incorporation of N into the material using soft conditions and low temperature.

Title: Crystallization of TiO2 nanotubes by in situ heating TEM
Authors: Alberto Casu 1, Andrea Lamberti 2, Stefano Stassi 2, and Andrea Falqui 1,*
Affiliation:
1 King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering (BESE) Division, NABLA Lab, 23955-6900 Thuwal, Saudi Arabia
2 Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
Abstract: The thermally-induced crystallization of TiO2 amorphous nanotubes so far has been studied under standard pressure conditions by techniques such as differential scanning calorimetry and in situ X-Ray diffraction, then looking at the overall response of several thousands of nanotubes. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, directly imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under standard pressure conditions, under the microscope's high vacuum the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures when the in situ heating was performed irradiating the sample with an electron beam energy of 120 or 300 keV, being such temperatures 450 °C and 380 °C, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy.

Title: Thermally stimulated currents in nanocrystalline titanium dioxide
Authors: Mara Bruzzi 1,*, Riccardo Mori 2, Ennio Carnevale 3, Monica Scaringella 4, and Franco Bogani 3
1 Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
2 Albert-Ludwigs-Universität Freiburg, Experimentelle Teilchenphysik, Physikalisches Institut, Hermann-Herder Straße 3, 79104 Freiburg im Breisgau, Germany
3 Dipartimento di Ingegneria Industriale, Università di Firenze, Via S. Marta 1, 50139 Firenze, Italy
Abstract: A set of nanocrystalline TiO2 (nc-TiO2) films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, in view to perform a detailed thermally stimulated currents (TSC) analysis in a broad temperature range. Fractional TSC spectra in the temperature range 5-300K have been measured after illuminating the sample with a UV led at liquid He temperature. Data have been processed by means of a numerical simulation considering both free and localized carrier contributions. The numerical procedure takes into account of a density of states (DOS) characterized by an exponential tail of localized states joined to a parabolic density of extended states. Results show that hopping gives the main contribution to electrical conduction, with a density of defect states around 10^20cm-3 and an exponential band-tail energy constant around 50 meV. TSC analysis has been also carried out in the temperature range 300-625K after storage in selected controlled atmosphere conditions, to elucidate the role of adsorbed water vapour molecules and of vacancy-oxygen defects to the conduction mechanisms.

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